Diaphragm for talking-machine sound-boxes.



- F.1 GUBELMAM DIAPHRAGIVI FOR TALKING MACHINE SOUND BOXES.

APPLICAVTION F\LED 1ULY7..191,7. 1,27 9, 10%., Pawmedsept. 17,1918

Uhl PATENT FFQE.

FREDEBICK J'. GUBELMAN, OF ENGLEWOOD, NEW JERSEY, ASSIGNOR T0 THE REGINA COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF NEW' JERSEY.

DLFLPHRAGM FOR TALKING-MACHINE SOUND-BOXESl Specification of Letters Patent. PaQm-td Sept 17, glg

.Application led July i, 191'?. Serial No. 179,174.

To all @cham t may concern Ee it known that I, Fimonmoxd. GUBEL- MAN, a citizen ot' the United States, residing at Englewood, .llero'en county, State of New Jersey, have invented certain new and use- Atill lmprfnfcments in lliaphragms for Talk- .shall reproduce vocal, musical and other tones ot' whatever pitch or character without chattering, blasting or other unpleasant sound ei'ects and in accurate correspondence with the sound impulses which are to be reproduced.

Another object of rnv invention is to pro-v vide a diaphragm Jfor the purpose described which can be definitely standardized as to dimensions and other physical charac- `teristics and which shall, withal, be simple and economical to construct and easily assembled into operative relations with its associated parts.

My invention will be better understood by referring to the accompanying drawings in which Figure l represents a central longitudinal section through a sound box containing a preferred form ot' diaphragm according tomy invention; Fig. 2 is a view similar to Fig. l showing a modification of my invention, certain parts common to the two ligures being omitted; Fig. 3 is a view similar to Figs. 1 and 2` showing still another modification ot the invention; Fig. 4 represents the diaphragm of Fig. 3 before it has been mounted in the sound box and before its parts have been clamped together in operative position. and Fig. 5 is a plan view looking from below of Fig. 8.

Referring to the drawings, l is the sound box casing having the usual tube :2 for connection to the tone arm anda circular recess or chamber El to receive the diaphragm 4 which is preferably a fiat mica disk of suitable thickness; any suitable material usual in the art may, however, be employed instead ot mica.

In the form of the invention shown in Fig. l the recess 3 isprovided with a peripheral outwardly convexed shoulder 5 against which the disk 4 is forced by a clamp ring which has threaded engagement with threads 7 formed on the inner Wall of casing 1. This results in a convexing of and a consequent stretching and stiffering ot' the disk.

A screw 8 astens the-center of the-disk tov one end of an operating lever 9 whose outer cud is twisted and bent so as to be attached to the rim of the casing 1. A thinned region 10 provides a fulcrum about which the lever 9 can oscillate. This operating lever 9 itself supports. at l1 one arm of a bell crank lever l2 which is arranged to rock about anaxis transverse to said arm and 70 mounted upon the casing 1, thus actuating the stylus 18 which is held by the other arm of the bell crank lever in correspondence with the movements of the diaphragm.

ln operation it will befound that the diaphragm is sensitive to a greater degree and more accurately responsive to vibratory impulses to which it may be subjected than is the case with diaphragm of the usual type when simply held or supported at their edges without' internal stiffening or stretch-- ing as just described.

It is believed that the improved results' produced by my novel diaphragm are due to the same reasons which cause superior' results to be produced by a well stretched drum head over that produced by a'locsely stretched drum head.

ln the form of the invention shown in Fig. 2 the shoulder at the bottom of recess 3 is square to the axis of the recess, butl the mica disk isclamped against it between an inner rubber ring or washer 14 and an outer rubber ring l?) of substantially larger diameter. The result is to force the outer periphery of the disk inwardly and to bow or convex the disk 4 4outwardly as in the form of Fig; 1. The diaphragm 4 is simi* larly stretched and st-iil'ened.'n

The diaphragm in the `form of my inven 100 tion shown in Figs. 3, 4 ando has clamped toit upon its rear side a comparatively sniall diametcred concave disk of aluminum 16 of about thesame thickness. The screw 8 in this case passes through both aluminum and mica disk and has its end threaded into' one end of the operating lever 9 as before. In this form of the invention, howevhr, the

'screw 8 is intended not merely to hold the quisite bowing, stiii'eningl and stretching of the diaphragm. It should, hence, be set or Idrawn up suiliciently to bring about a concaving or eupping of the mica disk'within he area covered by the aluminum disk. This results in arconsequent stretching and stiil'ening 'of the entire disk which is, therefore, made more sensitive and more accuf ratel responsive to vibratory impulses to whic it may be subjected. ,The aluminum cup is also greatly stretched and stlfened.

*The two disks sliouldnot, however, be so acter which engages the interior threads 7 and presses the diaphragm against a soft rubber ring 17 which rests up0n` the bottom of the box. A rubber washer 18'is prefthe diaphragm.

I find that chattering and -blasting is completely eliminated in sound boxes having diaphragms as above described. l Variations of detail may be made by those skilled in the art within the spirit and scope of the following claim: In a sound box, the combination of a casing, a diaphragm held in said casing, a stylus arranged to rock with lrespect to said casing anda lever operatively connected between stylus and' diaphragm,- said phragm comprising a plate of larger di- Ineter and a central cup with periphery in contact with the plate and its center drawn forcibly toward the plate thereby dishing the plate and flattening the cup. v

ln testimony whereof, I have hereunto set my hand.

FREDERICK J. GUBELMAN.

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